JP7152019B2 - Optical element and image display device using the same - Google Patents

Description

The present invention relates to an optical element that forms a real image of an observed object on one side in a space on the other side, and an image display apparatus using the optical element.

An optical element has been devised in which a projection object is placed on one side of a plane that partitions a space, and a mirror image of the projection object is formed at a plane-symmetrical position on the other side of the space. . An optical element of this type is known which has a structure in which a plurality of dihedral corner reflectors, each of which is composed of two minute mirror surfaces (reflection surfaces) perpendicular to each other, are aggregated in a plane (see, for example, Patent Document 1).

The above Patent Document 1 discloses an optical element having a dihedral corner reflector array in which a plurality of dihedral corner reflectors are arranged in a grid pattern on one plane. In this optical element, each mirror surface forming a dihedral corner reflector is arranged perpendicular to the element surface of the optical element. Therefore, the light emitted from the object to be observed arranged on one side of the element surface is reflected twice by the dihedral corner reflectors when passing through the optical element, and is bent. A real image is formed in the space on the side. Thereby, a real image of the observed object is formed such that the observed object exists at a symmetrical position with respect to the element plane of the optical element.

JP 2011-191404 A

In the optical element described in Patent Document 1, a plurality of cubic projections projecting from the surface of the substrate are arranged, and the inner walls of the projections are mirror surfaces, and the total reflection of light on the inner walls is used. Then, a real mirror image is formed. Here, the projecting portions are formed by providing grid-like grooves between adjacent projecting portions (dihedral corner reflectors). With such a configuration, part of the light incident on the substrate is guided to the groove side without being incident on the projecting portion. Among the light emitted from the object to be observed, the light incident on the mirror surface at an incident angle smaller than the critical angle is guided to the groove side without being reflected by the mirror surface. Such light guided to the groove side becomes stray light that does not contribute to the formation of the real mirror image, and lowers the contrast of the stereoscopic image. In addition, since the grooves between the dihedral corner reflectors are fine on the order of μm, when environmental light such as external illumination light is incident on the grooves, the light is irregularly reflected by the grooves, causing white blurring.

The present invention is intended to solve the above-mentioned problems, and suppresses stray light that does not contribute to the formation of a real mirror image, improves the contrast of a stereoscopic image, and suppresses diffuse reflection of light between a plurality of dihedral corner reflectors. An object of the present invention is to provide an optical element capable of reducing white blurring and an image display device using the same.

In order to solve the above-mentioned problems, the present invention provides an optical element that forms a real image of an object to be observed on one side in a space on the other side, the substrate being formed of a transparent material and forming a plane. and a plurality of protrusions formed integrally with the base so as to protrude from the base, wherein the protrusions have three or more side surfaces that are angled with respect to the base. Two adjacent side surfaces of the side surfaces are perpendicular to the base and substantially orthogonal to each other, and form a dihedral corner reflector that reflects light emitted from the observed object, and the plurality of protrusions are formed. A low refractive index portion made of a medium having a refractive index lower than that of the transparent material forming the protrusions and a light absorbing portion absorbing light guided between the plurality of protrusions are provided between the protrusions. and are arranged, the low refractive index portion is air and is in contact with the dihedral corner reflector, the light absorbing portion is composed of particles with a diameter of 1 to 10 μm, and is at least on the base It is in contact with the bottom surface of the groove between the adjacent protrusions in the groove .

In the above optical element, it is preferable that the low refractive index portion has a thickness of 1 μm or more from the surface of the dihedral corner reflector.

In the above optical element, it is preferable that the light absorbing portion is in contact with a side surface of the projecting portion that does not form the dihedral corner reflector.

The above optical element further includes a transparent panel covering the plurality of protrusions collectively, and the light absorbing portion is formed in a region of the transparent panel facing between the plurality of protrusions. preferably.

It is preferable that the optical element is used in a video display device.

According to the present invention, in the optical element, since the low refractive index portion is in contact with the side surface forming the dihedral corner reflector, the difference in refractive index from the medium constituting the optical element is increased, the total reflection efficiency is improved, The real mirror image can be brightened. In addition, since the light absorbing portion is provided between the projecting portions, the light guided between the projecting portions is cut, thereby suppressing the generation of stray light that does not contribute to the formation of the real mirror image. The contrast of the real mirror image can be improved. Furthermore, since the light absorbing portion cuts off ambient light such as external illumination light, the light is not diffusely reflected between the fine protrusions, and the occurrence of white blurring can be suppressed.

1 is a schematic perspective view conceptually showing a configuration example of an optical element according to a first embodiment of the present invention; FIG. 4(a) and 4(b) are diagrams schematically showing image formation modes by the optical element. FIG. The perspective view which expanded a part of said optical element. (a) is a side view of the optical element, and (b) is a top view. FIG. 4 is a side view for explaining the action of the optical element; (a) and (b) are side views for explaining a configuration and a forming method thereof according to a first modification of the optical element. (a) is a side view for explaining a configuration and a method of forming the same according to a second modification of the optical element, and (b) is an enlarged view of a dashed-dotted line region of (a). The side view for demonstrating the structure which concerns on the 3rd modification of the said optical element, and its formation method. The side view for demonstrating the structure which concerns on the 4th modification of the said optical element, and its formation method. FIG. 2 is a perspective view conceptually showing a configuration example of an image display device including the optical element.

An optical element according to one embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical element 1 of this embodiment has a dihedral corner reflector 30 made up of mirror surfaces (vertical surfaces 31 and 32) that are perpendicular to the substrate 2 and substantially perpendicular to each other. A plurality of dihedral corner reflectors 30 are arranged in a grid pattern on one plane of the substrate 2 to form a dihedral corner reflector array 30S.

When the object to be observed O is placed on one surface side of the optical element 1, the optical element 1 focuses a real image (real mirror image P) of the object to be observed O on the space on the other side of the element surface 1S of the optical element 1. make an image That is, the optical element 1 forms a real mirror image P of the observed object O at a plane-symmetrical position with the element surface 1S as a plane of symmetry. Here, the element surface 1S is a virtual plane perpendicular to the two vertical surfaces 31 and 32 forming the dihedral corner reflector 30. FIG. Note that the dihedral corner reflectors 30 are microscopic, on the order of μm, compared to the overall size of the optical element 1, which is on the order of cm or m. It is conceptually indicated by a character shape.

The imaging mode by the dihedral corner reflector array 30S will be described with reference to FIGS. 2(a) and 2(b). In FIG. 2A, it is assumed that the light emitted from the point light source o as the object to be projected travels three-dimensionally from the back side of the page to the front side of the page. Light (solid line arrow) emitted from a point light source o is reflected by one mirror surface (vertical surface 31) constituting the dihedral corner reflector 30 when passing through the optical element 1 (not shown in FIG. 2(a)). Then, after being reflected by the other mirror surface (vertical surface 32), it is transmitted through the element surface 1S (see FIG. 2(b)). The light emitted from the optical element 1 in this way (one-dot chain line arrow) passes through the element surface 1S while spreading at a plane-symmetrical position p of the point light source o. That is, the light transmitted through the optical element 1 is converged at a plane-symmetrical position p of the point light source o with respect to the element surface 1S and forms a real mirror image P (see FIG. 1).

As shown in FIGS. 3 and 4(a) and (b), the substrate 2 is made of a transparent material and forms a single plane. The optical element 1 has a plurality of protrusions 3 formed to protrude from the base 2 . The plurality of protrusions 3 are integrally formed with the base 2 from the same transparent material as the base 2 .

The protrusion 3 has three or more side surfaces that are angled with respect to the base 2 . The projecting portion 3 of the present embodiment has a truncated pyramid shape, and two surfaces perpendicular to the base 2 (vertical surfaces 31 and 32) and two surfaces inclined with respect to the base 2 (inclined surfaces 33 and 34) and an upper surface 35 forming a plane parallel to the base 2 . Of the side surfaces, two vertical surfaces 31 and 32 are adjacent to each other, and two inclined surfaces 33 and 34 are adjacent to each other. Moreover, the vertical surfaces 31 and 32 are arranged so as to be substantially perpendicular to each other. Light (solid line arrows in FIG. 4A ) incident on the projecting portion 3 from the substrate 2 is totally reflected twice by the inner wall surfaces of the vertical surfaces 31 and 32 and emitted from the upper surface 35 of the projecting portion 3 .

The upper surface 35 is defined by the ridgelines of the vertical surfaces 31, 32 and the inclined surfaces 33, 34, and has substantially the same length, and is substantially square in top view (see FIG. 4(b)). The vertical surface 31 (32) has, in a side view (see FIG. 4(b)), a boundary line (dotted line in FIG. 4(a)) with the base 2 as the lower base, a ridgeline with the upper surface 35 as the upper base, and an inclined surface. It is a trapezoid whose oblique side is the edge line with 33 and 34 and whose vertical side is the edge line with the adjacent vertical surfaces 32 and 31 .

On the surface of the optical element 1, a plurality of protrusions 3 having the shape described above are arranged in a grid pattern. The adjacent projecting portions 3 have one vertical surface 31 and the other inclined surface 34 opposed to each other, and one vertical surface 32 and the other inclined surface 33 to each other. In other words, the plurality of projecting portions 3 have grid-like grooves 21 formed between the vertical surfaces 31 and 32 and the inclined surfaces 34 and 33 facing each other. In addition, a surface parallel to the substrate 2 is formed between the side of the vertical surface 32 (31) facing the substrate 2 and the side of the inclined surface 33 (34) facing the substrate 2, and the bottom of the groove 21 is formed. A bottom surface 22 is formed.

Further, the optical element 1 includes the grooves 21 between the plurality of protrusions 3, the low refractive index portions 4 made of a medium having a lower refractive index than the transparent material forming the protrusions 3, and the grooves 21. A light absorbing portion 5 that absorbs waved light is arranged. The low refractive index portion 4 is in contact with at least the vertical surfaces 31 and 32 forming a dihedral corner reflector.

The medium of the substrate 2 and projections 3 constituting the optical element 1 is made of a transparent material that has a light transmittance of 80% or more, a refractive index of 1.3 or more, and is less susceptible to deterioration due to heat and humidity. Examples of such transparent materials include acrylic resin and glass. In the optical element 1 of the present embodiment, it is particularly preferable to use a cycloolefin polymer (COP), which is a hydrocarbon-based polymer having a low water absorbency, an amorphous structure, and an alicyclic structure. Examples of cycloolefin polymers include ZEONOR (registered trademark) manufactured by Nippon Zeon Co., Ltd. (grade: 1020R, light transmittance of 92%, refractive index of 1.53). In addition, the low refractive index portion 4 preferably has a medium with a refractive index of 1.4 or less in order to reduce the critical angle at the vertical surfaces 31 and 32 to facilitate total reflection. , the medium of the low refractive index portion 4 is air.

When manufacturing the optical element 1 of the present embodiment, first, a portion other than the low refractive index portion 4 and the light absorbing portion 5, that is, a dihedral corner reflector array 30S composed of the base 2 and a plurality of projecting portions 3 is manufactured. be. Examples of the method of manufacturing the dihedral corner reflector array 30S include a method of injection molding translucent resin using a mold such as a stamper, or a hot press molding method. The mold is produced, for example, by forming shapes corresponding to the shapes of the projections 3 and the grooves 21 (see FIG. 3) on the metal master plate by nano-machining, and then reversing the balls. In addition, for example, by using X-ray lithography, it is possible to produce the projection 3 having four sides and the groove 21 directly in the substrate 2 made of a transparent material.

In the optical element 1 of this embodiment, two of the four surfaces forming the projecting portion 3 are the inclined surfaces 33 and 34 . That is, the projecting portion 3 has a truncated pyramid shape. A bottom surface 22 is provided in the groove 21 between the plurality of adjacent projecting portions 3 . With such a shape, it is possible to add a so-called "draft taper" to the projecting portion 3, which is a fine structure on the order of μm. The dihedral corner reflector array 30S can be easily removed from a mold such as a stamper.

The width W of one side of one pitch of the protrusions 3 including the grooves 21 when viewed from above is, for example, 100 to 700 μm (see FIG. 4B). Note that the pitch width W is set according to the projection distance of the real mirror image P (see FIG. 1). For example, when the protruding distance is 10 cm, the pitch width W is approximately 280 μm. The plate thickness of the optical element 1 including the base 2 and the protrusions 3 is generally 1 to 3 mm. A height H (depth of the groove 21) from the base 2 (bottom surface 22 of the groove 21) of the projecting portion 3 is set equal to or larger than the pitch width W.

The inclination angle θ of the inclined surfaces 33, 34 with respect to the normal to the base 2 is preferably 5 to 25° (see FIG. 4(a)). By setting the inclination angle θ to 5° or more, it is possible to secure a necessary draft taper and facilitate removal from the mold when manufacturing the dihedral corner reflector array 30S. In addition, by setting the inclination angle θ to 25° or less, the size (width L) of the upper surface 35, which is the emission surface of the light reflected by the dihedral corner reflector 30, depends on the height H of the projecting portion 3. can be ensured, and darkening of the real mirror image P can be suppressed. It is assumed that the height H of the projecting portion 3 is 300 μm, the width W of one side of the projecting portion 3 when viewed from the top is 300 μm, the width L of one side of the upper surface 35 is 200 μm, and the inclination angle θ is 18°. In this case, the width D of the bottom surface 22 of the groove 21 is approximately 2.5 μm. Note that the numerical values shown here are representative values shown as an example of the present embodiment, and the present invention is not limited to these numerical values.

The optical element 1 of this embodiment is obtained by further forming the low refractive index portion 4 and the light absorbing portion 5 on the dihedral corner reflector 30 manufactured as described above. For example, black ink or particulate pigment is used for the light absorbing portion 5 . Moreover, the low refractive index portion 4 preferably has a thickness of 1 μm or more from the surfaces of the vertical surfaces 31 and 32 forming the dihedral corner reflector 30 . The low refractive index portion 4 is formed so that the portion having a thickness of 1 μm or more from the surface of the vertical surfaces 31 and 32 forming the dihedral corner reflector 30 is 50% or more of the total area of the vertical surfaces 31 and 32. It is good if it is. When the light is totally reflected by the vertical surfaces 31 and 32 forming the dihedral corner reflector 30, if there is a medium with a high refractive index on the outside of the vertical surfaces 31 and 32 with an interval of about the wavelength of the light, an evanescent wave light is transmitted through the vertical surfaces 31 and 32, and total reflection on the inner wall surfaces of the vertical surfaces 31 and 32 may be suppressed. Therefore, on the outside of the vertical surfaces 31 and 32, the low refractive index portion 4 having a thickness of 1 μm or more is arranged at least in a region where the evanescent wave can seep out, covering 50% or more of the total area of the vertical surfaces 31 and 32. , the decrease in the total reflection efficiency can be suppressed, and the decrease in the luminance of the real mirror image P can be prevented.

As a method of forming the low refractive index portion 4 and the light absorbing portion 5, for example, a method of applying ink containing a light absorbing material toward the inclined surface 33 (34) and the bottom surface 22 of the groove 21 by micro-inkjet printing. is mentioned. In this way, the ink applied to the inclined surface 34 (33) and the bottom surface 22 of the groove 21 becomes the light absorbing portion 5, and air exists on the vertical surface 31 (32) side where the ink is not applied. , the space in which the air exists becomes the low refractive index portion 4 . As long as there is no practical problem, the inclined surfaces 34 (33) and the grooves 21 may be unevenly coated, and the vertical surfaces 31 (32) may be slightly coated with ink.

In the optical element 1 produced in this way, as shown in FIG. The difference in refractive index from the medium that constitutes 1 is increased. Therefore, the critical angle on the vertical surface 32 becomes small, and even light with a small incident angle α (solid line arrow in the drawing), which would not be totally reflected if there is no low refractive index portion 4, can be totally reflected. Improve efficiency. As a result, the real mirror image P can be brightened.

Further, since the light absorbing portions 5 are provided between the projecting portions 3, the light incident on the substrate 2 is guided from the bottom surface 22 to the groove 21 side without being incident on the projecting portions 3. The light (broken line arrow in the drawing) is cut by the light absorbing portion 5 . In addition, the light that is incident on the vertical surface 32 at an angle of incidence smaller than the critical angle and is transmitted to the groove 21 (one-dot chain line arrow in the drawing) is also cut. In this way, since the light guided to the groove 21 side is cut by the light absorbing portion 5, it is possible to suppress the occurrence of stray light that does not contribute to the imaging of the real mirror image P, and the contrast of the real mirror image P can be reduced. can be improved.

The grooves 21 between the dihedral corner reflectors 30 are micrometer-order, but even if ambient light (double-dot chain line arrows in the figure) such as external illumination light between them enters the grooves 21, the light Since the absorption part 5 cuts the light, the minute grooves 21 do not diffusely reflect the light, and the occurrence of white blurring can be suppressed.

Preferably, the light absorbing portion 5 is in contact with the side surfaces of the projecting portion 3 that do not form the dihedral corner reflector 30, that is, the inclined surfaces 33 and 34 in this embodiment. A part of the light incident on the projecting portion 3 from the base 2 may be incident on the inclined surfaces 33 and 34 instead of the vertical surfaces 31 and 32 . This light also does not contribute to the formation of the real mirror image P, and becomes stray light that reduces the contrast of the real mirror image P when guided to the groove 21 side. Therefore, by arranging the light absorbing portion 5 so as to be in contact with the inclined surfaces 33 and 34, the light guided to the groove 21 side can be cut.

The configuration of the low refractive index portion 4 and the light absorption portion 5 and the method of forming the same are not limited to those described above. Modifications relating to the configurations of the low refractive index portion 4 and the light absorption portion 5 and a method for forming the same will be described below.

As a first modification, as shown in FIG. 6(a), a film of a removable seal material Rm having a thickness of 1 μm is formed on the vertical surface 32 (31) in advance, and the groove 21 is formed with the light absorbing material Am. A forming method of removing the sealing material Rm after filling and curing the filled light absorbing material Am can be mentioned. According to this forming method, as shown in FIG. 5(b), a gap having a thickness of about 1 μm is provided from the vertical surface 32 (31) in the space where the seal material Rm was formed. The refractive index portion 4 is formed, and the light absorbing material Am filled except for the gap becomes the light absorbing portion 5 . This forming method includes, for example, a method of removing only the sealing material Rm by immersing them in a predetermined solvent in which the light absorbing material Am does not dissolve but the sealing material Rm dissolves.

Also in this first modification, since the low refractive index portion 4 is in contact with the vertical surface 32 (31) forming the dihedral corner reflector 30, the total reflection efficiency is improved, and the real mirror image P can be brightened. can. Further, since the light absorbing portions 5 are provided between the projecting portions 3, stray light can be suppressed and the contrast of the real mirror image P can be improved. Furthermore, in the first modified example, compared with the configuration example shown in FIG. , the occurrence of white blurring can be effectively suppressed.

As a second modification, as shown in FIG. 7A, there is a method of filling grooves 21 between a plurality of projecting portions 3 with substantially spherical light absorbing particles 5s. For example, a resin, carbon, or the like is used for the light absorbing particles 5s, and particles obtained by encapsulating carbon black in crosslinked polymer fine particles are particularly preferable. The lower limit of the particle size of the light absorbing particles 5s is 1 μm or more, preferably 2 μm or more. The upper limit of the particle size of the light-absorbing particles 5s is at least smaller than the maximum width of the grooves 21, and is preferably 10 μm or less in consideration of the filling properties into the grooves 21. FIG.

In this second modification, some of the light absorbing particles 5s also adhere to the vertical surface 32 (31). However, as shown in FIG. 7(b), since the light absorbing particles 5s are substantially spherical, there are only a few contact points between the light absorbing particles 5s and the vertical surfaces 32 (31). There are many gaps (air) between. Therefore, this gap functions as the low refractive index portion 4 . As described above, in the low refractive index portion 4, the portion having a thickness of 1 μm or more from the surfaces of the vertical surfaces 31 and 32 forming the dihedral corner reflector 30 accounts for 50% or more of the total area of the vertical surfaces 31 and 32. The thickness of the low refractive index portion 4 may partially be 1 μm or less. According to the second modification, the low refractive index portions 4 and the light absorbing portions 5 are formed by a simple method of filling the grooves 21 between the plurality of projecting portions 3 with substantially spherical light absorbing particles 5s. can do. Further, as in the above configuration example, stray light that does not contribute to the formation of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and diffuse reflection of light between the plurality of dihedral corner reflectors 30 is suppressed. White blur can be reduced.

As a third modification, as shown in FIG. 8, a transparent panel 6 that collectively covers the plurality of projecting portions 3 is further provided, and the light absorbing portion 5 is arranged on the plurality of projecting portions of the transparent panel 6. 3 can be formed in a region facing the groove 21 between them. Glass, acrylic resin, or glass and a transparent material are used for the transparent panel 6 .

In this forming method, for example, the pattern of the grooves 21 between the plurality of projecting portions 3 is scanned, and the same pattern is printed on the transparent panel 6 with a light-absorbing material (ink) to form the plurality of projecting portions 3. After precisely aligning with the groove 21 between them, they are stuck together. As long as there is no practical problem, the printed pattern may be slightly different from the actual groove pattern, and there may be some positional deviation during lamination. For example, the width of the printed groove pattern may have an error of about ±20 μm compared to the actual width of the groove 21, and the positional deviation during lamination may be about ±20 μm.

In the third modification, the space surrounded by the grooves 21 between the plurality of projecting portions 3 and the light absorbing portions 5 formed on the transparent panel 6 serves as the low refractive index portion 4 . In the third modification, similarly to the configuration example described above, stray light that does not contribute to the imaging of the real mirror image P is suppressed to improve the contrast of the stereoscopic image, and a plurality of It is possible to suppress the diffuse reflection of light between the dihedral corner reflectors 30 and reduce the white blurring.

Further, in each of the configuration examples described above, it was necessary to form the light absorbing portions 5 three-dimensionally in the grooves 21. Since printing is performed on the shaped transparent panel 6, the light absorbing portion 5 can be formed substantially two-dimensionally, and the low refractive index portion 4 and the light absorbing portion 5 can be formed easily.

In a fourth modified example, as shown in FIG. 9, the projecting portion 3 is a cube, and the inclined surfaces 33 and 34 in the above configuration example are not present, and the side surfaces of the projecting portion 3 are 4 All of the surfaces are vertical surfaces (vertical surface 36 in the illustrated example). The low refractive index portion 4 is also provided on the vertical surface 36 side. In the configuration example having the inclined surfaces 33 and 34 described above, the light emitted from the object O (see FIG. 1) in the direction facing the interior angle of the vertical surfaces 31 and 32 is reflected twice by the vertical surfaces 31 and 32. so that the real mirror image P is formed. On the other hand, in this fourth modification, even light from the direction opposite to the internal angle of the vertical surfaces 31 and 32 is reflected by the dihedral corner reflectors of the vertical surface 36 and the vertical surface (not shown) orthogonal thereto. Then, a real mirror image can be formed.

Next, a video display device according to an embodiment of the invention will be described with reference to FIG. The image display device 10 is a specific application of the optical element 1 described above, and includes a box 12 having an opening 11 on the upper surface and an image display section 13 provided on the inner surface of the box 12. Prepare. The optical element 1 is attached to the opening 11 of the box 12 . In the illustrated example, the image display unit 13 uses, for example, a liquid crystal display device, and in the illustrated example, the character "A" is displayed in an upside-down posture. Light emitted from the image display unit 13 is bent and reflected by the optical element 1 to form a real mirror image of the letter "A". When an observer looks into the optical element 1 with the viewpoint Ep positioned diagonally above the image display device 10, the observer can visually recognize the real mirror image of the letter "A" as an aerial image.

The present invention is not limited to the above embodiments and various modifications, and various modifications are possible. In the above embodiment and modified examples, the projecting portion 3 has a truncated pyramidal shape or a cubic shape having four side surfaces, but it has two vertical surfaces and an upper surface for emitting light. For example, a truncated triangular pyramid shape or a truncated pyramid shape with five or more angles may be used. Further, if the light absorbing portion 5 exists between the plurality of projecting portions 3 so that the low refractive index portion 4 is formed between the vertical surfaces 31 and 32, the light absorbing portion 5 is not necessarily limited to the configuration example described above. can't In addition, it is most preferable that the main medium of the low refractive index portion 4 is air, which has a low refractive index. Silica particles or the like may be applied as appropriate.

REFERENCE SIGNS LIST 1 optical element 10 video display device 2 base 3 projecting portion 30 dihedral corner reflector 31, 32 vertical plane (side surface)
33, 34 Inclined surface (side surface)
4 low refractive index portion 5 light absorbing portion 5s light absorbing particles (particles)
6 transparent panel

Claims (5)

An optical element that forms a real image of an object to be observed on one side in a space on the other side,
a base made of a transparent material and forming a single plane; and a plurality of protrusions formed integrally with the base so as to protrude from the base,
The projecting portion has three or more side surfaces that are angled with respect to the base,
Two adjacent side surfaces of the side surfaces are perpendicular to the base and substantially orthogonal to each other, forming a dihedral corner reflector that reflects light emitted from the object to be observed,
A low refractive index portion made of a medium having a refractive index lower than that of a transparent material forming the protrusions and absorbing light guided between the protrusions. and a light absorbing portion that
the low refractive index portion is air and is in contact with the dihedral corner reflector;
The optical element according to claim 1, wherein the light absorbing portion is composed of particles having a diameter of 1 to 10 μm, and is in contact with at least the bottom surface of the groove between the adjacent protrusions on the substrate. 2. The optical element according to claim 1, wherein the low refractive index portion has a thickness of 1 [mu]m or more from the surface of the dihedral corner reflector. 3. The optical element according to claim 1, wherein the light absorbing portion is in contact with a side surface of the projecting portion that does not form the dihedral corner reflector. further comprising a transparent panel that collectively covers the plurality of protrusions;
4. The optical element according to any one of claims 1 to 3, wherein the light absorbing portion is formed in a region of the transparent panel facing between the plurality of projecting portions. . An image display device using the optical element according to any one of claims 1 to 4.

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